Production of alkali metal and alkaline earth metal hydroxides



Patented Apr. 13, 1948 raoovonouomtimm mEiEARTBiME mnoxmcs Dane \Wickerhmmbar, W; Vat; ,assienoo to;

mericana Deb, a-

. nnorati .11.

vi cesee. onnotat on):

of aware ilminatom,

Application- Noyember;10, 1945; SerialNo;-- 6211;914* eqaimst. (o1. 2a-184) comprises anovel combine-flow of stepsforming a cyclic. 'processwh'avingz importanttadivantages in:

that it isweconomicatand resuttssin products, which are usable in the formcihcwhich;they=1areobtained. F01 instance; whea -the processiis practiced in connection with sedition-sulfide, the product is sodium:- hydroxide which may has directly used in the:preparationlotaviscosel Sula furic acid 'mayxalso be obtained, asa byproduct;- and in a condition suitable for use baths used in the manufacture OffiibGPS' or other articles from viscose in accordance With-the :wet spinning process; Y i

Basically the process of. my: invention-5 com. prises, in combinatiom the stcps of (a) :rea m of the selectedisulfi'deof an alkali m-eta'lfoaelite. line earth metalwith the aqueous; m complex-0f a metal hlyclroxide tofoim'an alk li metal hydroxide and precipitateathe metal oi the ammonium complex assulfide (b)-recove1:yof aqueous ammonia from thereductiom solution: (c) separationof thl metal-sulfide:precipitated in step a) and oxidation -1 thereof to-rthe metaloxide, (d)- reaction of the metal oxide aqueous ammonia fromstep (b') to we form the aqueous ammoniumcomplex o t1ie-= metal h-ydroxide: and return of the lii-ttei to=step -(a) fen treatment of freshquantiti'e's of the alkali'imewt or alkaline earth-metal'sulfide, andHe-Jcencen tration of the alkali metal 01 alkalineearth-m eta/l hydroxide solution rem-aini'n aftep separationof the metal sulfide and removal r 0f the amm-onia Steps (Z7) and (c) maybe carried out in -ei-theh order or simultaneously if" desired. Also the oxide ofsulfur obtained by: oxidation of themetal' sulfide separated 1 from the alkali metal or, alkaline earth metal hydroxide sol-utiom may be workedup in anyway; For example;- it may' -b'e: further oxidized i to sulfur trioxide and absorbed in a concentrated or dilute solution of sulfui'ia acid; l

Metal ammoniumcomplexes: Which-are suit! able for use in accordancewvith-this inventionaro cuprammonium hydroxide, nickel: ammonium hydroxide, cadmium ammonium hydroxide; (JG-rt balt ammonium. hydroxide,- silverxammonium hydroxide, zinc ammonium hydroxide etc;

Preferably, the metal is one havingan: oxide which does-not form anions inlthepresemwe of alkali metal hydroxide solution and: which is solublein aqueous; ammonia: with formation-mi:

2-. the metal hydroxide. The preferred e metals are further characterizedin that theyfo m sulfides which are precipitated'in the presence of aqueous ammqnia and sodium, hydroxide solution and which axe: oxidizable to sulfur-dioxide or trioxidewitlgregenerationiot the ammoniaqsoluble metal oxides,

he a ompan i w e n the at rez of ow: sheets, will illustrate the nv on as anpliegkto sodium sulfideand using; the ammonium complex :01;- copper, Thesodium; sulfide may be obtained by reduction of sodium sulfate bymeans f; e uitable. r duc naa ent: h a s. wa bon hydrocarbonanatural or manutactured gas etc.

usuallmthetpmductt o btained swa com anied y mpaxativ yesmall amounts f dium.sul: f to *whichdmay; bet desimbleh th u h n t. 5111" tial, since the,-,sodiumtsuliatesma l fu ction as a flux during the step ot reductionsto sodiu sulef heea ka itm tall su fide is not acc m-l p i y s um-l uliatel, tt may, be; admixed herewith, or with other agents which function as-a-iflux; ast o: nstance, an alkaiilmetalocanbos ate-orih droxide,

Referr ngt s tis 1,] of the, draw n od um.

suhat t wh ch mean he th x ess, al l m v dl from, the=- acid ospinnin at siorl viscos lemumanuiact r dx. ntr uced nt t melt r it ismmucedgtol so iumlsulfldee he. reilati n roduc wh h. m y, omm-r e ome. sodium suliate; is next, led. i to; an alka izer. wheret slrea t d with. for? xamule, cunmmmon ..h dr oxide ta noducee diumh roxide. nd. opper-- sulfideo The. rea tion. proce ds. a follows;v

nne 's lfidez sasub tae .-;Za-1.1y ii- 0 1 ar a thez cdiwx hyd s .oden o'lu i uw .e i eci te Itris: senatratedt rom-t-he une mti t 1 u dsaedl f0 W813flQ 0;a dchydrat t'h. time, bein undue-ted: to b" e steam: s: injected; Ammo a.

Wat rr are in crystallizer 8, filtered oil and. returned to smelter 2. The residue consists of a concentrated sodium hydroxide solution which is suitable for use, for example, in the preparation of viscose. Any traces of copper remaining in the solution may be precipitated by the addition of small amounts of such substances as glucose, hemi-cellulose or other-reducing agents, priorto the step of evaporation. In those instances where sodium carbonate is present in admixture with the sodium hydroxide it may be removed by treating the mixture with calcined lime.

The copper sulfide dehydrator 4 is fed into a roaster 9, where it is oxidized to copper oxideand sulfur dioxide, the copper oxide being separated, and'introduced into converter 6, where it reacts cordance with the invention, an economical and valuable method is provided for disposing Of the large amounts of sodium sulfate obtained as byproduct in the rayon industry. The concentration of the sodium sulfate normally present as a constituent of such baths is continuously built up during spinning or casting procedures so that eventually the baths contain excessively large amounts of sodium sulfate, disposition of which usually entails either dispatch thereof to a waste disposal system or conversion of Glaubers salt with the aqueous ammonia recovered from the 5 sodium hydroxide solution, additional water being added, as required, to re-iorm cuprammonium hydroxide in accordance with the following equation:

The cuprammonium hydroxide thus obtained is returned to alkalizer 3. The sulfur dioxide is further oxidized to sulfur trioxide in contact converter id, and the S03 is absorbed in cc-ncen trated sulfuric acid in a conventional type of ahsorption tower I [to produce fuming sulfuric acid which, on dilution, is ready for use in setting baths such as are used in the rayon industry, or for any other purpose.

Oxidation of the sulfur dioxide to sulfur tri-- oxide may be effected in the presence of any suitable catalyst which promotes the reaction between S02 and oxygen. The S03 gases issuing from the contact converter may be cooled, if desired, as by passage thereof through heat exchangers, to avoid decomposition ba'ckto S02 and oxygen, and to render theabsorption of the S03 in sulfuric acid more efficient.

Referring now to Fig. 2, which, illustrates a modification of the invention in which the steps of the process are carried out in a different order, the sodium sulfide, is obtained by reduction of sodium sulfate in the smelter l2. The product leaving the smelter, and which comprises, some sodium sulfate, is filtered to separate the sulfate, after which it is introduced into the alkalizer is,

where it is treated with, for example, cuprammonium hydroxide, to produce sodium hydroxide and copper sulfide, after which it is forwarded to a boiler i4 into which steam is injected. Ammonia and water are volatilized and thevapors are condensed and introduced into a converter I5. The copper sulfide which settles out is filtered from the solution by means of filter i6, forwarded to a dehydrator I1 and then fed into a roaster [8 where it is oxidized to copper oxide and sulfur dioxide, the copper oxide being separated and sent to converter I5 for reaction with the aqueous ammonia previously recovered, to re-form cuprammonium hydroxide which is recycled to alkalizer I3. The residue from the copper sulfide separation comprises a sodium hydroxide solution, which may be concentrated in an evaporator i9.

Although the invention is of general application to sulfides of the alkali metaland alkaline earth metals as a class, it is of particular value for the conversion of sodium sulfide to a c0n-' centrated solution of sodium hydroxide and suliuric acid, since by reduction of the sodium'sulfate recovered from viscose setting baths, and treatment of the resultant sodium sulfide in. ac-

to anhydrous sodium sulfate by methods requir- 1 ing complicated evaporating devices with attendant difficulties due to incrustation of the evaporating surfaces by deposited salt crystals. The present invention provides a method for converting the sodium sulfate, through the corresponding sulfide, to products which are directly reuseable in the form obtained, in the manufacture of rayon fibers or other articles from viscose, thus effecting a substantial saving in the ultimate costs of rayon manufacture. The oxidation of the metal sulfide to the oxide, at one stage of the process, and reaction thereof with aqueous ammonia recovered at another stage, is a particularly valuable feature of the invention, since when the oxide and aqueous ammonia are reacted together as indicated by the equation set forth above, the aqueous ammonium complex of the metal hydroxide is reformed and is recirculated for reaction with fresh alkali metal or alkaline earth metal sulfide, the process being continuously operated with extremely small losses.

I claim:

1. A process for obtaining hydroxides of metals selected from the group consisting of alkali metals and. alkaline earth metals from sulfides of the corresponding alkali metals and of the alkaline earth metals which comprises the step of reacting the selected sulfide with the aqueous ammon um complex of a metal hydroxide regenerated by reaction of water, ammonia and metallic oxide obtained from the product of reaction between sulfide and aqueous ammonium complex of the meta1 hydroxide at an earlier stage of the process.

2. A process for obtaining hydroxides of metals selected from the group consisting of alkali metals and alkaline earth metals from sulfides of the corresponding alkali metals and of the alkaline earth metals which comprises the step of reacting the selected sulfide with cuprammonium hydroxide regenerated by reaction of water, ammonia and copper oxide obtained from the product of reaction between sulfide and cuprammonium hydroxide at an earlier stage of the process.

3. A process for obtaining sodium hydroxide from sodium sulfide which comprises the step of reacting the sulfide with the aqueous ammonium complex of a metal hydroxide regenerated by reaction of water, ammonia and metallic oxide obtained from the product of reaction between sodium sulfide and the aqueous ammonium complex of the metal hydroxide at an earlier stage of the process.

4. A process for obtaining sodium hydroxide fldes of the corresponding alkali metals and of the alkaline earth metals which comprises reacting the selected sulfide with the aqueous ammonium I complex of a metal hydroxide to form a solution of the alkali metal or alkaline earth metal hydroxide and precipitate the metal of the ammonium complex in the form of its sulfide, separating the metal sulfide from the solution of the alkali metal or alkaline earth metal hydroxide, oxidizing the separated metal sulfide to the metal oxide, recovering aqueous ammonia from the hydroxide solution separated from the metal sulfide, reacting the metal oxide with the recovered aqueous ammonia to re-form the aqueous ammonium complex of the metal hydroxide, and recycling the latter for reaction with fresh alkali metal or alkaline earth metal sulfide.

6. A cyclic method for obtaining sodium hydroxide from sodium sulfide, which comprises reacting the sodium sulfide with the aqueous ammonium complex of a metal hydroxide to form a solution of sodium hydroxide and precipitate the metal of the ammonium complex in the form of its sulfide, separating the metal sulfide from the sodium hydroxide solution and oxidizing the metal sulfide to the metal oxide, recovering aqueous ammonia from the hydroxide solution separated from the metal sulfide, reacting the metal oxide with the recovered aqueous ammonia to re-form the aqueous ammonium complex of the metal hydroxide, and recycling the latter for reaction with fresh sodium sulfide.

7. A cyclic process for obtaining sodium hydroxide from sodium sulfide, which comprises reacting the sodium sulfide with cuprammonium hydroxide to form sodium hydroxide and precipitate copper sulfide, separating the copper sulfide from the sodium hydroxide solution and oxidizing the copper sulfide to copper oxide, recovering aqueous ammonia from the hydroxide solution, separated from the copper sulfide, reacting the copper oxide with the recovered aqueous ammonia to re-form cuprammonium hydroxide, and recycling the latter for reaction with fresh sodium sulfide.

8. A cyclic process for obtaining hydroxides of metals of the group consisting of alkali metals and alkaline earth metals, from the sulfides of the corresponding alkali metals and of the alkaline earth metals, which comprises reacting the selected sulfide with the aqueous ammonium complex of a metal hydroxide to form a solution of the alkali metal or alkaline earth metal hydroxide and convert the metal of the aqueous ammonium complex to its sulfide, then separating the metal sulfide, subjecting the residue to a boil-off to vaporize ammonia and water therefrom and condensing the vapors, oxidizing the metal sulfide to the metal oxide, reacting the metal oxide with the recovered aqueous ammonia to re-form the aqueous ammonium complex of the metal hydroxide, and recycling the latter for reaction with fresh alkali metal or alkaline earth metal sulfide.

9. A cyclic process for obtaining hydroxides of metals selected from the group consisting of alkali metals and alkaline earth metals, from. sulfides of the corresponding alkali metals and of the alkaline earth metals, which comprises reacting the selected sulfide with the aqueous ammonium complex of a metal hydroxide to form a solution of the alkali metal or alkaline earth metal hydroxide and convert the metal of the ammonium complex to its sulfide, then subjecting the reaction product to a boil-oil to vaporize ammonia and water therefrom and condensing the Vapors,

then separating the metal sulfide and oxidizing it to the metal oxide, reacting the metal oxide with the recovered aqueous ammonia to re-form the aqueous ammonium complex of the metal hydroxide, and recycling the latter for reaction with fresh alkali metal or alkaline earth metal. sulfide.

DAN B. WICKER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 823,896 Ranson June 19, 1906 2,164,141 Moore June 27, 1939 2,145,815 Morrow Jan, 31, 1939 2,175,273 Mertes Oct. 10, 1939 2,173,912 Mertes Sept, 26, 1939 OTHER REFERENCES Inorganic and Theoretical Chemistry, by Mellor, vol. 3 (1923), page 151.

Certificate of Correction v Patent No. 2,439,404. April 13, 1948. g DAN B. WICKER i It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Column 3, line 13, after the word sulfide insert leaving; and that the said Letters Patent should be read with this coirii'ection therein that the same may conform to the record of the case in the Patent 0 co.

Signed and sealed this 15th day of June, A. D. 1948.

THOMAS F. MURPHY,

Assistant Gommicioner of Patents. 

